Wireless transmit/receive units (WTRUs) may be equipped with receive antenna diversity. For example, certain receiver types in the Third Generation Partnership Project (3GPP) requirements may be designed with the assumption of receive diversity. Furthermore, in technical specifications, such as in Release 7 (R7) of the 3GPP Wideband Code Division Multiple Access (WCDMA) Frequency Division Duplex (FDD) specifications, support for downlink multiple-input multiple output (MIMO) operations has been defined. In R7 MIMO, for example, spatial multiplexing is achieved by means of two antennas at the transmitter, (e.g., Node-B) and two antennas at the receiver, (e.g. WTRU). Due to the potential high data rate achievable with MIMO receivers and the performance increase resulting from receive diversity alone, it is possible that the number of WTRUs built with two receive antennas increases over the years.
However, while WTRUs may be built with multiple antennas for receive diversity and MIMO operations, there is currently no method for the WTRU to transmit using spatial diversity. Doing so may potentially provide increased uplink (UL) coverage, as well as system-level gains due to lower interference. Therefore, it would be beneficial to provide a method and apparatus for performing uplink transmit diversity.